To be scientifically snarky, CAH is an autosomal recessive disorder. There is no one gene that causes CAH, but rather two mutated alleles that disrupt enzyme production that cause CAH.
To use some crazy genetics terms, remember that a gene is made up of two alleles. Sometimes, one allele for a particular trait is dominant over another allele- for example, the allele for brown eyes is dominant over the allele for blue eyes. However, genes coding for enzyme production (in the case of CAH, the enzyme 21 hydroxylase) the alleles work a little differently. Both of the alleles will code for enzyme production- unless there is someone wrong with one of the alleles!
For example, I am a carrier of CAH. That means that my gene that is responsible for producing 21 hydroxylase has one allele for normal production of 21 hydroxylase and one allele that does not have the correct ‘code’ to produce 21 hydroxylase. So, I suppose, you could think that the allele that codes for normal 21 hydroxylase production as being the ‘dominant’ allele. In reality, what it is going on is that the one allele for normal 21 hydroxylase production makes up for the allele that can’t produce it.
In CAH, you have two alleles that cannot code for 21 hydroxylase. For example, my child inherited one set of alleles from me and one set of alleles from her father (two alleles make a gene, right?!) She just happened to receive the faulty alleles for 21 hydroxylase production from both her father and I- therefore, she produces no 21 hydroxylase and has SWCAH.
Hope this helps!
Martha